Automated optical inspection (AOI) systems are typically employed in the inspection of electrical circuits, including Printed Circuit Boards (PCBs), flat panel displays, chip carriers, integrated circuits and the like. Some known AOI systems operate based on a single illumination configuration that is typically configured for detecting specific types of defects. Other known AOI system operate using a plurality of illumination configurations to allow detection of a wider range of defects.
Commercially available AOI systems include the Inspire™ 9060 using color images, Discovery™ and V-300™ systems for inspecting bare PCBs, the Trion™ system for inspecting populated PCBs, FPI-6090™ and FPI-7590™ systems for inspecting flat display panels, and ICP 8060™ system for inspecting chip carriers. All of the above systems were or are commercially available from Orbotech Ltd. of Yavne, Israel.
U.S. Pat. No. 7,397,552 entitled “Optical inspection with alternating configurations”, the contents of which is incorporated herein by reference, describes an imaging system for inspection of a wafer including an illumination module providing pulsed optical radiation and a mechanical scanner arranged to scan an area of the surface irradiated by the illumination module and to irradiate a plurality of successive, substantially overlapping frames on the surface by respective successive pulses of the pulsed radiation, each said successive frame having an overlap with a respective preceding frame of at least 50%. The imaging system includes a system controller, arranged to vary a configuration of the imaging system in alternation between a first configuration and a second, different, configuration, whereby the sequence of images comprises at least a first set of images captured in the first optical configuration and a second set of images captured in the second optical configuration. The imaging system includes an image processor, arranged to jointly process the first image and the second image to detect a defect in the sample by analyzing features on the surface as imaged using each of the first and the second optical configurations.
U.S. Pat. No. 6,781,687 entitled “Illumination and Image Acquisition System” assigned to Orbotech Ltd., the contents of which is incorporated herein by reference, describes an inspection system that illuminates a surface of an electrical circuit with flashes of light. The flashed light is from at least two spectrally different sources temporally spaced. Each flash is incident on the surface at the same location and generally the same angle of incidence. A camera forms a separate optical image from each flash of light. The images formed with the different flashes are combined to form a full view image. Analysis of the full view image is performed to determine defects in the electric circuit.
US Patent Application Publication No. US2002/0186878 entitled “System and Method for Multiple Image Analysis”, the contents of which is incorporated herein by reference, describes a system for analyzing multiple images to locate defects in a test component. The system includes first and second light sources each emitting a different color light from a different angle and a camera with a processor to generate two or more images. The images are used to construct a 3-dimensional image of the object and are then analyzed to determine whether a dimension of the test component is acceptable.
The Amethyst™ system commercially available by Orbotech Ltd. of Yavne, Israel provides for sequentially acquiring several images of an area with different illumination as described in http://www.orbotech.com/D2_ProductsGroup.asp?MenuID=566 (Nov. 16, 2008).